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The Differences between All Wheel Drive and Four Wheel Drive


Published October 24, 2018

The terminology can be confusing, as some manufacturers may have one vehicle they market as All-Wheel Drive (AWD) and another they market as Four-wheel Drive (sometimes written as 4WD or 4x4).

So whether it's an AWD or a 4WD system, you know that power is being delivered to all four wheels in a low traction situation, a clear advantage over traditional two-wheel drive vehicles, whether they are Front-wheel Drive (FWD) or Rear-wheel Drive (RWD) either of which are driving just a single axle.

The difference between AWD and 4WD can sometimes be a little confusing, especially since AWD systems have become more capable and 4WD systems have become more sophisticated, making the dividing line between the two a little murky. Adding to the confusion, a system that manufacturer A defines as AWD is sometimes described by manufacturer B as 4WD. But in reality, it's less about how the system operates and more about how it fits with how you drive.
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What Is All Wheel Drive?
All-wheel drive systems power both the front and rear wheels either some or all of the time, depending upon the system. These are considered either Full-time AWD or Part-time AWD. They're typically found in vehicles that are also offered in a FWD version, there's a drive shaft that runs to the rear axle to power the two back tires. The purpose, in either case, is better traction on slippery road surfaces. In Full-time AWD, both the front and rear axles are driven all the time. This system is becoming less popular as the additional drag of the Full-time system impacts fuel economy. In contrast, a Part-time AWD utilizes sensors to recognize wheel slip and automatically engages the other two wheels when encountering rain-, snow-, or ice-covered roads. These systems also have mild off-road capabilities, for example driving down a muddy road.

Advantages and Disadvantages of All Wheel Drive
With AWD systems either all the wheels are being driven full-time, or the system itself senses a loss of traction and sends power to the other wheels. AWD is available on a wide variety of vehicles, from compact sedans to performance models to all sizes of SUVs, giving you a broad range of choices.
The two disadvantages of an AWD system is that first, it will cost more on the same vehicle than the two-wheel drive version, and second, especially in the case of full-time AWD, you will pay a penalty at the gas pump. However, automatic part-time systems have managed to recover much of the mpg loss of a full-time system.

What Is Four-Wheel Drive?
This is the more traditional system of driving all four wheels and has been in use for over 100 years. Heavy trucks, construction equipment, and military transports have long utilized 4WD systems. What's different about 4WD systems is that they deliver power through a series of front, rear and center differentials, transfer cases and couplings, which provides maximum traction under a range of conditions.

Part-time 4WD systems are what you think of in a traditional off-road vehicle. These systems have low and high 4WD ranges that can be selected by the driver, either via an electronic switch or a floor-mounted mechanical lever. The low setting locks all the wheels together to provide maximum traction in an off-road environment. This can only be used at low speeds as it doesn't allow for the difference in turning speeds between the inside and outside wheels. So there's a high setting that's used for extended driving in slippery conditions like snow, ice, sand or gravel. For dry conditions, the driver can disconnect one axle (typically the front) so that the vehicle now operates in two-wheel drive mode.

Full-time 4WD operates similar to that of a full-time AWD system, with all four wheels receiving power on a continuous basis. In some designs, the driver may have the option of controlling how power is apportioned to the front and rear axles through selectable modes, which are predetermined settings in the vehicle's computer that adjusts various inputs such as throttle, steering, and brake to optimize traction in specific conditions.

Advantages and Disadvantages of Four-Wheel Drive
4WD vehicles are generally best at handling low-traction conditions, both on road and off. Even though these systems are available in well-appointed trucks and luxury SUVs, at heart they still tend to be designed for ruggedness and maximum pulling power, and they are well-suited for work and play in difficult terrain. However, they are the most costly and will typically offer lower fuel economy than their 2WD counterparts.

Which System is Best for You?
It's all a matter of trade-offs. If you're simply looking for a vehicle that can handle the snow, sleet, and ice of winter and you're only driving on paved roads, then an AWD system may well fulfill your requirements. On the other hand, if you're into outdoor sports, a more versatile system that provides the driver with more control could provide better performance pulling a boat out of the water or maneuvering down sandy trails. Your best advice is to come and talk to the experts at Automaxx Kalamazoo, share with them your needs and intended use, and they'll help you select the vehicle that best meets your needs.
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